This section provides background information related to the present disclosure which is not necessarily prior art.
Various refrigerants have been utilized in refrigeration systems that include a compressor machine, such as a scroll compressor or a reciprocating compressor. For example, halogenated hydrocarbon compounds have been widely used as refrigerants. Halogenated hydrocarbons tend to be stable, inert in their interaction with lubricants used in the compressor machine, and tend to have operating envelopes at moderate temperatures and pressures. However, halogenated hydrocarbons also have high global warming potential (a relative measure of how much heat a greenhouse gas traps in the atmosphere), so that these refrigerants have the potential to be environmentally detrimental if any leaks from refrigeration systems should occur.
In recent years, tightening environmental regulations have prompted significant interest and development in compressors and refrigeration systems that use refrigerants having low global warming potential. Thus, development of compressor designs that use natural or more environmentally-friendly refrigerants has been ongoing. One such refrigerant is carbon dioxide (CO2 or R-744), which has a desirably low global warming potential of 1. Another is propane (C3H8 or R-290) having a global warming potential of less than about 4.
Compressors using carbon dioxide refrigerant typically require extremely high pressures (e.g., 30 to 200 atmospheres) and temperatures to operate in a refrigeration cycle. Compressors using CO2 refrigerant may operate on a subcritical, transcritical or supercritical cycle under various operating conditions. In such operations, the CO2 is particularly corrosive and may behave as a solvent or corrosive agent, penetrating and attaching a surface of a material or component inside the compressor causing undesirable reactions, resulting in corrosion, embrittlement, and the like. Propane can also behave as a solvent under certain conditions, thus causing similar issues, like corrosion. Further still, prevalent conventional refrigerants that contain halogens, particularly chlorides, tend to provide greater lubricity between parts. However, in the case of CO2 or C3H8 as refrigerants, such benefits are absent. Moreover, hermetic compressor designs may pose particular design challenges, as they typically cannot be disassembled for regular maintenance of internal parts. Thus, failure or degradation of certain components can end a hermetic compressor's service life.
There is therefore a need for compressors that use carbon dioxide refrigerant, or alternatively propane, especially scroll compressors or reciprocating compressors, where the components exposed to refrigerant have greater wear and corrosion resistance, as well as improved anti-friction properties. Accordingly, the present disclosure is directed to a durable compressor machine and a reciprocating compressor which is designed to operate efficiently and to have improved wear and corrosion resistance when operated with the harsh operating conditions associated with a CO2 refrigerant or alternatively C3H8 refrigerant.